CN106339554B - A kind of excavation of foundation pit causes the calculation method of neighbouring existing Subway Tunnel Displacement - Google Patents
A kind of excavation of foundation pit causes the calculation method of neighbouring existing Subway Tunnel Displacement Download PDFInfo
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Abstract
The present invention provides the calculation method that a kind of excavation of foundation pit causes neighbouring existing Subway Tunnel Displacement, specifically comprise the following steps: first to establish computation model, carry out hole bottom unloading analysis, foundation pit side-wall unloading analysis is carried out again, finally by utilize principle of stacking, obtain the unloading stress generated by Foundation Pit bottom and surrounding side wall, certain point (x on the outside of caused tunnel1,y1,z1) horizontal total displacement SxWith vertical total displacement Sz；To accurately calculate caused tunnel lateral displacement under Foundation Pit bottom load and surrounding side wall load action, the half side tunnel towards foundation pit side is taken, respectively several points, calculate separately the shift value of this several points, finally take average shift value as Tunnel Displacement value.Therefore the construction of concrete engineering can be simulated by this patent method before constructing, calculates the Subway Tunnel Displacement size under specified operating condition, if tunnel is more than corresponding permissible value, can adjust associated construction parameter and carry out tentative calculation, until reaching safety standard.
Description
Technical field
The present invention relates to the calculation methods that a kind of excavation of foundation pit causes neighbouring existing Subway Tunnel Displacement, belong to underground engineering
Technical field.
Background technique
(1) forefathers or consider surrounding crater wall stress release effect.Since Mindlin solution is only applicable to elastic half-space
Body after excavation of foundation pit, can only calculate displacement caused by the crater wall stress of adjacent piles side；Crater wall stress far from tunnel side
It is imponderable due to that cannot be transmitted by the soil body (having excavated).Therefore it is analyzed in terms of calculation method, considers surrounding crater wall
Stress is problematic.
(2) or only consider the crater wall stress of adjacent piles side.It theoretically analyzes, only considers the crater wall stress of side,
It will lead to the increase of Tunnel Displacement and coverage, therefore also unreasonable.
(3) or the side wall additional stress that excavation of foundation pit generates is equivalent to triangular load, size are as follows:
K0γz
In formula: K0For coefficient of static earth pressure；
γ is the severe of soil, unit symbol kN/m3；
Z is the vertical distance calculated point from the ground, unit symbol mm.
This method does not account for the supporting role of foundation pit enclosure structure, causes side wall additional stress bigger than normal.
(4) or the hole subsoil body stress release that excavation of foundation pit generates is equivalent to upward rectangle evenly load, size
Are as follows:
Γd；
In formula: d is excavation of foundation pit depth, unit symbol mm.
The assumed condition, which is only applicable to bottom of foundation ditch or less, does not have the operating condition of building enclosure.
And have building enclosure below most of bottom of foundation ditch, the shielding effect of bottom of foundation ditch building enclosure is not accounted for, i.e.,
The equivalent load of bottom of foundation ditch can not be applied directly on adjacent piles.
(5) or tunnel structure is considered as elastic foundation Infinite Beam, only assumes that there is the effect of soil body spring in side.
Tunnel is acted in the soil body by surrounding confining pressure, i.e., should there be soil body spring in upper and lower, left and right, rather than only side
Have.Therefore tunnel not generates integral level movement, and surface displacement is all different, and existing method can not calculate the water in tunnel
It puts down to convergency value.
Summary of the invention
With the development and utilization of urban subway tunnel, the house property construction in area along the line is driven, has caused foundation pit increasingly
Close to subway tunnel.
Soil deformation caused by Unloading necessarily will drive tunnel structure and generate displacement, and over-large displacement will affect tunnel
The stabilization of road structure, to influence the normal operation of subway train.
Therefore, it is of great significance to the displacement prediction of neighbouring existing subway tunnel caused by excavation of foundation pit.
The invention patent considers the shadow of foundation pit enclosure structure by establishing simplified excavation of foundation pit mechanics model
It rings, is solved using Mindlin, derive the calculation formula of neighbouring existing tunnel displacement caused by Foundation Pit bottom and crater wall off-load.
To achieve the above object, present invention employs technical solutions below:
The calculation method that a kind of excavation of foundation pit causes neighbouring existing Subway Tunnel Displacement is provided, it is contemplated that:
(1) there is building enclosure to protect (including the borehole wall and inner support or outer support) when excavation of foundation pit, therefore will not all unload
It carries；The side wall equivalent addition stress calculation formula that excavation of foundation pit generates is should be multiplied by a reduction coefficient β, in which: β encloses for foundation pit
The stress loss rate of protection structure, equal to the ratio of the side wall stress and initial sidewall stress that finally discharge, β < 1；
Then equivalent load becomes: β K0γz；
It is considered as the collective effect of four side walls, enables the β value of four side walls identical；
(2) since shield tunnel rigidity is larger, shield tunnel table caused by the soil mass of foundation pit stress release of close tunnel side
Earth horizontal displacement S1 (towards foundation pit side) at face, significantly larger than tunnel horizontal displacement S；
The stiffness in tunnel, it is assumed that there is spring to hold the soil body at shield tunnel surface, or to tunnel surface
The soil body at place is applied with an opposition, it is made to generate a reversed displacement S2 (far from tunnel side)；
The two superposition, final result is to lead to tunnel horizontal displacement coverage and tunnel maximum horizontal displacement value, small
Soil body S1 at shield tunnel surface；
(3) this patent is while calculating the residual stress of the soil body at foundation pit enclosure structure bottom plane, it is also contemplated that power exists
The frictional resistance of building enclosure side wall influences when transmitting downwards；
(4) this patent will calculate the shift value of half of tunnel surface of neighbouring foundation pit side, and the displacement for making a concrete analysis of tunnel becomes
Change, obtains the horizontal direction convergency value in tunnel；
Specifically comprise the following steps:
Step 1) establishes computation model: (computation model is shown in Fig. 1)
1., 2., 3. and 4. the number of four side walls of foundation pit is respectively；
Foundation pit length L, unit symbol mm；
Foundation pit width B, unit symbol mm；
From foundation pit central point o transversely and horizontally with a distance from be x, be 1. positive with o point to side wall, unit symbol mm；
It is y with a distance from vertical equity from o point, is 3. positive with o point to side wall, unit symbol mm；
Distance d of the excavation of foundation pit face bottom to foundation pit enclosure structure bottom surface0, unit symbol mm；
The minimum clear distance s, unit symbol mm of excavation face and tunnel；
Foundation pit enclosure structure depth H, H=d+d0, unit symbol mm；
Vertical distance h, unit symbol mm of the ground to tunnel bottom；
Tunnel outer diameter D, unit symbol mm；
Calculation assumption:
(1) soil body is homogeneous, elastic half-space, and tunnel axis is oriented parallel to the long side of rectangle foundation pit；
(2) time and the space factor for not considering excavation of foundation pit, do not consider precipitation；
(3) when excavation of foundation pit to hole bottom when will lead to resistance to shear of soil release, be converted into hole baseplane at apply vertically to
On evenly load γ d；
(4) foundation pit surrounding side wall can generate stress release after excavation, be equivalent to apply the triangle into hole in side wall
Horizontal direction distributed load β K0γz；
(5) do not consider that tunnel has the influence calculated additional stress of soil；
(6) by considering that the foundation pit side-wall far from tunnel side discharges stress, to replace tunnel stiffness；
Step 2), hole bottom unloading analysis:
Due to the protective effect of bottom of foundation ditch building enclosure, the stress for forming shielding effect, therefore cheating bottom release, which will receive, to be enclosed
The side friction that protection structure generates influences, the side friction calculation formula are as follows:
qs=c+K0σztanφ；
In formula:
qsFor unit equivalent entity side friction, unit symbol Pa；
C is the cohesive strength of soil, unit symbol Pa；
σzFor the soil stress at the arbitrary face at Foundation Pit bottom to building enclosure bottom, unit symbol Pa；
φ is the internal friction angle of soil, and unit symbol is °；
According to actual condition, it is changed to average side friction calculation formula are as follows:
qs1=c+1/2 (γ d+ γ H) K0tanφ；
In formula:
qs1Mean unit side friction, unit symbol Pa；
As shown in Fig. 2, the equivalent load that then soil body is subject at the horizontal plane of foundation pit enclosure structure bottom surface are as follows:
In formula:
σ is the equivalent load that the soil body is subject at the horizontal plane of foundation pit enclosure structure bottom surface, unit symbol Pa；
α is residual stress coefficient；
By the basic displacement solution of Mindlin vertical load, by integral, certain point on horizontal plane at the building enclosure bottom surface
Under the unit force σ d ξ d η effect of (ξ, η), certain point (x on the outside of caused tunnel1,y1,z1) horizontal displacementWith vertical displacementIt is respectively as follows:
In formula:
ξ is that certain puts abscissa, unit symbol mm on horizontal plane at building enclosure bottom surface；
η is that certain puts ordinate, unit symbol mm on horizontal plane at building enclosure bottom surface；
μ is the Poisson's ratio of soil；
G is the coefficient of rigidity of soil,Unit symbol is Pa；
EsFor the compression modulus of soil, unit symbol Pa；
Step 3), foundation pit side-wall unloading analysis:
It is foundation pit side-wall Triangle-Profile 1. in number by integrating by the basic displacement solution of Mindlin horizontal loading
The unit force β K of certain point (η, τ) in load0Under γ d η d τ effect, cause certain point (x on the outside of tunnel1,y1,z1) horizontal displacementWith vertical displacementIt is respectively as follows:
In formula:
τ is the ordinate of certain point in the foundation pit side-wall Triangle Load Distribution of number 1., unit symbol mm；
In the case where number is foundation pit side-wall Triangle Load Distribution effect 2., cause certain point (x on the outside of tunnel1,y1,z1)
Horizontal displacementWith vertical displacementIt is respectively as follows:
In formula:
In the case where number is foundation pit side-wall Triangle Load Distribution τ effect 3., cause certain point (x on the outside of tunnel1,y1,z1)
Horizontal displacementWith vertical displacementIt is respectively as follows:
In formula:
In the case where number is foundation pit side-wall Triangle Load Distribution effect 4., cause certain point (x on the outside of tunnel1,y1,z1)
Horizontal displacementWith vertical displacementIt is respectively as follows:
In formula:
Step 4), total calculation formula:
Using principle of stacking, the unloading stress generated by Foundation Pit bottom and surrounding side wall, caused tunnel outside are obtained
Certain point (x1,y1,z1) horizontal total displacement SxWith vertical total displacement SzIt is respectively as follows:
To accurately calculate caused tunnel lateral displacement under Foundation Pit bottom load and surrounding side wall load action, court is taken
To the half side tunnel of foundation pit side, respectively several points, calculate separately the shift value of this several points, and average shift value is finally taken to make
For Tunnel Displacement value.
The theoretical basis of this patent is sturdy, has studied excavation of foundation pit and causes neighbouring existing Subway Tunnel Displacement calculation formula.
It can be according to specific site operation parameter, such as coefficient of static earth pressure K before construction0, soil severe γ, excavation of foundation pit
Depth d, foundation pit length L, foundation pit width B, the distance d of excavation of foundation pit face bottom to foundation pit enclosure structure bottom surface0, excavation face and tunnel
The minimum clear distance s in road, foundation pit enclosure structure depth H, the vertical distance h on ground to tunnel bottom, tunnel outer diameter D, native is viscous
Poly- power c, native internal friction angleResidual stress factor alpha, soil Poisson's ratio μ, for soil Modulus of pressure Es, simulate different parameters
Under execution conditions, excavation of foundation pit may be to the displacement of neighbouring existing subway tunnel generation.
In a practical situation, engineering construction has strict control to Tunnel Displacement size, if Tunnel Displacement is more than corresponding allows
, then there is engineering safety hidden danger in value, or even cause the serious consequences such as surface subsidence, surrounding building inclination, underground utilities destruction.
Therefore the construction of concrete engineering can be simulated by the formula of this patent, is calculated under specified operating condition before constructing
Subway Tunnel Displacement size can adjust associated construction parameter if tunnel is more than corresponding permissible value and carry out tentative calculation, until reach peace
Full standard.
This patent causes neighbouring existing Subway Tunnel Displacement size to carry out in advance by theoretical formula, to practical excavation of foundation pit
It surveys, there is prevention, directive function to engineering, and provide for the research for influencing aspect to adjacent piles in relation to excavation of foundation pit from now on
Theoretical basis.
Detailed description of the invention
Fig. 1 is the front view of the computation model in the present invention；
Fig. 2 is the right view of the computation model in the present invention；
Fig. 3 is the top view of the computation model in the present invention；
Fig. 4 is the load schematic diagram in computation model in the present invention at foundation pit enclosure structure bottom surface；
Fig. 5 is that horizontal displacement change curve in tunnel caused by four side wall off-loads is illustrated in computation model in the present invention
Figure；
Fig. 6 is the contrast schematic diagram of length of tunnel and excavation of foundation pit length in the present invention.
Specific embodiment
A specific embodiment of the invention is made a detailed explanation with reference to the accompanying drawing.
As shown in figs. 1 to 6, the present invention provides the calculation method that a kind of excavation of foundation pit causes neighbouring existing Subway Tunnel Displacement
Specific embodiment, due to consideration that:
(1) there is building enclosure to protect (including the borehole wall and inner support or outer support) when excavation of foundation pit, therefore will not all unload
It carries；The side wall equivalent addition stress calculation formula that excavation of foundation pit generates is should be multiplied by a reduction coefficient β, in which: β encloses for foundation pit
The stress loss rate of protection structure, equal to the ratio of the side wall stress and initial sidewall stress that finally discharge, β < 1；
Then equivalent load becomes: β K0γz；
It is considered as the collective effect of four side walls, enables the β value of four side walls identical；
(3) since shield tunnel rigidity is larger, shield tunnel table caused by the soil mass of foundation pit stress release of close tunnel side
Earth horizontal displacement S1 (towards foundation pit side) at face, significantly larger than tunnel horizontal displacement S；
The stiffness in tunnel, it is assumed that there is spring to hold the soil body at shield tunnel surface, or to tunnel surface
The soil body at place is applied with an opposition, it is made to generate a reversed displacement S2 (far from tunnel side)；
The two superposition, final result is to lead to tunnel horizontal displacement coverage and tunnel maximum horizontal displacement value, small
Soil body S1 at shield tunnel surface；
(3) this patent is while calculating the residual stress of the soil body at foundation pit enclosure structure bottom plane, it is also contemplated that power exists
The frictional resistance of building enclosure side wall influences when transmitting downwards；
(4) this patent will calculate the shift value of half of tunnel surface of neighbouring foundation pit side, and the displacement for making a concrete analysis of tunnel becomes
Change, obtains the horizontal direction convergency value in tunnel；
Specifically comprise the following steps:
Step 1) establishes computation model: (computation model is referring to Fig. 1~3)
1., 2., 3. and 4. the number for enabling four side walls of foundation pit is respectively；
Foundation pit length L, unit symbol mm；
Foundation pit width B, unit symbol mm；
From foundation pit central point o transversely and horizontally with a distance from be x, be 1. positive with o point to side wall, unit symbol mm；
It is y with a distance from vertical equity from o point, is 3. positive with o point to side wall, unit symbol mm；
Distance d of the excavation of foundation pit face bottom to foundation pit enclosure structure bottom surface0, unit symbol mm；
The minimum clear distance s, unit symbol mm of excavation face and tunnel；
Foundation pit enclosure structure depth H, H=d+d0, unit symbol mm；
Vertical distance h, unit symbol mm of the ground to tunnel bottom；
Tunnel outer diameter D, unit symbol mm；
Calculation assumption:
(7) soil body is homogeneous, elastic half-space, and tunnel axis is oriented parallel to the long side of rectangle foundation pit；
(8) time and the space factor for not considering excavation of foundation pit, do not consider precipitation；
(9) when excavation of foundation pit to hole bottom when will lead to resistance to shear of soil release, be converted into hole baseplane at apply vertically to
On evenly load γ d；
(10) foundation pit surrounding side wall can generate stress release after excavation, be equivalent to apply the triangle into hole in side wall
Horizontal direction distributed load β K0γz；
(11) do not consider that tunnel has the influence calculated additional stress of soil；
(12) by considering that the foundation pit side-wall far from tunnel side discharges stress, to replace tunnel stiffness；
Step 2), hole bottom unloading analysis:
Due to the protective effect of bottom of foundation ditch building enclosure, the stress for forming shielding effect, therefore cheating bottom release, which will receive, to be enclosed
The side friction that protection structure generates influences, the side friction calculation formula are as follows:
qs=c+K0σztanφ；
In formula:
qsFor unit equivalent entity side friction, unit symbol Pa；
C is the cohesive strength of soil, unit symbol Pa；
σzFor the soil stress at the arbitrary face at Foundation Pit bottom to building enclosure bottom, unit symbol Pa；
φ is the internal friction angle of soil, and unit symbol is °；
According to actual condition, it is changed to average side friction calculation formula are as follows:
qs1=c+1/2 (γ d+ γ H) K0tanφ；
In formula:
qs1Mean unit side friction, unit symbol Pa；
As shown in figure 4, the equivalent load that then soil body is subject at the horizontal plane of foundation pit enclosure structure bottom surface are as follows:
In formula:
σ is the equivalent load that the soil body is subject at the horizontal plane of foundation pit enclosure structure bottom surface, unit symbol Pa；
α is residual stress coefficient；
By the basic displacement solution of Mindlin vertical load, by integral, certain point on horizontal plane at the building enclosure bottom surface
Under the unit force σ d ξ d η effect of (ξ, η), certain point (x on the outside of caused tunnel1,y1,z1) horizontal displacementWith vertical displacementIt is respectively as follows:
In formula:
ξ is that certain puts abscissa, unit symbol mm on horizontal plane at building enclosure bottom surface；
η is that certain puts ordinate, unit symbol mm on horizontal plane at building enclosure bottom surface；
μ is the Poisson's ratio of soil；
G is the coefficient of rigidity of soil,Unit symbol is Pa；
EsFor the compression modulus of soil, unit symbol Pa；
Step 3), foundation pit side-wall unloading analysis:
It is foundation pit side-wall Triangle-Profile 1. in number by integrating by the basic displacement solution of Mindlin horizontal loading
The unit force β K of certain point (η, τ) in load0Under γ d η d τ effect, cause certain point (x on the outside of tunnel1,y1,z1) horizontal displacementWith vertical displacementIt is respectively as follows:
In formula:
τ is the ordinate of certain point in the foundation pit side-wall Triangle Load Distribution of number 1., unit symbol mm；
In the case where number is foundation pit side-wall Triangle Load Distribution effect 2., cause certain point (x on the outside of tunnel1,y1,z1)
Horizontal displacementWith vertical displacementIt is respectively as follows:
In formula:
In the case where number is foundation pit side-wall Triangle Load Distribution τ effect 3., cause certain point (x on the outside of tunnel1,y1,z1)
Horizontal displacementWith vertical displacementIt is respectively as follows:
In formula:
In the case where number is foundation pit side-wall Triangle Load Distribution effect 4., cause certain point (x on the outside of tunnel1,y1,z1)
Horizontal displacementWith vertical displacementIt is respectively as follows:
In formula:
Step 4), total calculation formula:
Using principle of stacking, the unloading stress generated by Foundation Pit bottom and surrounding side wall, caused tunnel outside are obtained
Certain point (x1,y1,z1) horizontal total displacement SxWith vertical total displacement SzIt is respectively as follows:
To accurately calculate caused tunnel lateral displacement under Foundation Pit bottom load and surrounding side wall load action, court is taken
To the half side tunnel of foundation pit side, respectively several points, calculate separately the shift value of this several points, and average shift value is finally taken to make
For Tunnel Displacement value.
The theoretical basis of this patent is sturdy, has studied excavation of foundation pit and causes neighbouring existing Subway Tunnel Displacement calculation formula.
It can be according to specific site operation parameter, such as coefficient of static earth pressure K before construction0, soil severe γ, excavation of foundation pit
Depth d, foundation pit length L, foundation pit width B, the distance d of excavation of foundation pit face bottom to foundation pit enclosure structure bottom surface0, excavation face and tunnel
The minimum clear distance s in road, foundation pit enclosure structure depth H, the vertical distance h on ground to tunnel bottom, tunnel outer diameter D, native is viscous
Poly- power c, native internal friction angleResidual stress factor alpha, soil Poisson's ratio μ, for soil Modulus of pressure Es, simulate different parameters
Under execution conditions, excavation of foundation pit may be to the displacement of neighbouring existing subway tunnel generation.
In a practical situation, engineering construction has strict control to Tunnel Displacement size, if Tunnel Displacement is more than corresponding allows
, then there is engineering safety hidden danger in value, or even cause the serious consequences such as surface subsidence, surrounding building inclination, underground utilities destruction.
Therefore the construction of concrete engineering can be simulated by the formula of this patent, is calculated under specified operating condition before constructing
Subway Tunnel Displacement size can adjust associated construction parameter if tunnel is more than corresponding permissible value and carry out tentative calculation, until reach peace
Full standard.
This patent causes neighbouring existing Subway Tunnel Displacement size to carry out in advance by theoretical formula, to practical excavation of foundation pit
It surveys, there is prevention, directive function to engineering, and provide for the research for influencing aspect to adjacent piles in relation to excavation of foundation pit from now on
Theoretical basis.
Wherein: the basic displacement solution of Mindlin horizontal loading:
In formula: S is land movement, unit symbol mm；
P is the horizontal concentrated force for acting on l depth, unit symbol N；
L is to calculate distance of the point away from earth's surface, unit symbol mm；
M is the distance between load point position to soil body settlement calculation point, unit symbol mm；
N be load point about ground symmetric points the distance between to soil body settlement calculation point, unit symbol mm.
The basic displacement solution of Mindlin vertical load:
Due to standard condition calculating parameter: it is assumed that certain foundation pit plane excavates the long L=20m of size, wide B=10m, cutting depth
D=15m, foundation pit enclosure structure depth H=27m.Subway tunnel outer diameter D=6.2m, tunnel bottom depth h=15m, excavation of foundation pit
Face and tunnel minimum clear distance are s=5m.Severe γ=18.5kN/m of soil3, coefficient of static earth pressure K0=0.53, native pressure
Contracting modulus Es=10MPa, native Poisson's ratio μ=0.35, native cohesive strength c=12kPa, native internal friction angleFoundation pit encloses
Stress loss rate β=25% of protection structure.
It is 0 that calculated result, which shows that the soil body under the mark condition at building enclosure bottom plane adds vertical load,.Due to vertical
Factor that load need to consider is complicated, influences vulnerable to foundation pit enclosure depth, precipitation etc., so this patent is by selective analysis excavation of foundation pit
The horizontal displacement of caused side existing tunnel changes.
As shown in figure 5, the variation of Tunnel Displacement caused by four side wall off-loads is different, 1. unloading stress promotes tunnel to side wall
Road is close to foundation pit side, side wall 2. then with 1. on the contrary, tunnel deformation can be reduced, illustrate 1. cause side wall when reinforcing weight
Depending on.Influence of the side wall 3. with unloading stress 4. to Tunnel Displacement is small, and in irregular variation.
The tunnel horizontal displacement value that this patent method is calculated, with tunnel Horizontal displacement monitoring value and finite element modelling
As a result make dimensionless comparative analysis, as a result see Fig. 6.It is as shown in the figure: (1) context of methods (considering four side walls) calculated value and actual measurement
It coincide very much with finite element modelling result, shows that semi analytic semiempirical solution proposed in this paper has certain reliability.If herein only
Consider side wall 1., it is clear that have a tremendous difference with the dimensionless curve of actual measurement and finite element, coverage is obviously bigger than normal；(2) tunnel
The drift displacement curve is in normal distribution substantially, and the coverage of tunnel horizontal displacement is about foundation pit along tunnel longitudinal direction excavation length L
2~3 times.The coverage marked under condition herein is about 2L (i.e. ± L), is kissed with the coverage of actual measurement and finite element modelling result
It closes.
In addition bibliography [1]~[7] are simply described as follows in Fig. 6:
[1] the provisional rule of subway technical management are protected in construction along Shanghai municipal engineering management board subway in Shanghai
The fixed Shanghai [S]: Shanghai municipal administration management board, 1994.
Shanghai Road Administration Bureau.The provisional rules of subway
technical management about protecting the building-construction along the
Subway lines in Shanghai [S] .Shanghai:Shanghai Municipal Management Bureau,
1994.
[2] influence [J] the geotechnical engineering journal of condition Longchuan deep foundation pit construction to subway tunnel, 2000,22 (3): 284-
288.
KUANG Long-chuan.Influence of construction of deep foundation pit on
tunnels of metro[J].Chinese Journal of Geotechnical
Engineering, 2000,22 (3): 284-288.
[3] site-test analysis [J] the underground space and engineering science that Shao Hua, Wang Rong excavation influence neighbouring subway
Report, 2011,7 (supplementary issues 1): 1403-1408.
SHAO Hua,WANG Rong.Monitoring data analysis on influence of operating
metro tunnel by nearly excavation construction[J].Chinese Journal of
Underground Space and Engineering, 2011,7 (Supp.1): 1403-1408.
[4] Gao Guangyun, Gao Meng, Yang Chengbin wait foundation pit construction to influence and control to study on the deformation of operation tactics
[J] geotechnical engineering journal, 2010,32 (3): 453-459.
GAO Guang-yun,GAO Meng,YANG Cheng-bin,et al.Influence of deep
excavation on deformation of operating metro tunnels and countermeasures[J]
.Chinese Journal of Geotechnical Engineering, 2010,32 (3): 453-459.
[5] numerical analysis [J] underground space that Zhou Jiankun, Li Zhihong influence tunnel deformation close to tunnel base pit engineering
With engineering journal, 2010,6 (supplementary issues 1): 1398-1403.
ZHOU Jian-kun,LI Zhi-hong.Numerical Analysis on deformation effect of
metro tunnels due to adjacent excavation project[J].Chinese Journal of
Underground Space and Engineering, 2010,6 (Supp.1): 1398-1403.
[6] Zou Jianan, Yang little Ping, Liu Tingjin analyze [J] railway construction adjacent to the deep foundation pit support of Shield-bored tunnels,
2013, (9): 63-67.
ZOU Jia-nan,YANG Xiao-ping,LIU Ting-jin.Analysis on retaining
structure of the deep excavation adjacent to metro tunnels[J].Railway
Engineering, 2013, (9): 63-67.
[7] Guo Dianta, Zhou Cuiying, Zhu Yuanhui excavation of foundation pit study the Guangdong [J] to the affecting laws of proximity subway tunnel
Building and building, 2014, (6): 16-19.
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Guangdong Architecture Civil Engineering, 2014, (6): 16-19.
Claims (1)
1. the calculation method that a kind of excavation of foundation pit causes neighbouring existing Subway Tunnel Displacement, which is characterized in that
(1) there is building enclosure protection when excavation of foundation pit, therefore will not all unload；Equivalent add of the side wall that excavation of foundation pit generates is answered
Power calculation formula is should be multiplied by a reduction coefficient β, in which: β is the stress loss rate of foundation pit enclosure structure, is equal to final release
Side wall stress and initial sidewall stress ratio, β < 1；
Then equivalent load becomes: β K0γz；
It is considered as the collective effect of four side walls, enables the β value of four side walls identical；
(2) since shield tunnel rigidity is larger, at shield tunnel surface caused by the soil mass of foundation pit stress release of close tunnel side
Earth horizontal displacement S1, significantly larger than tunnel horizontal displacement S；
The stiffness in tunnel, it is assumed that there is spring to hold the soil body at shield tunnel surface, or to tunnel surface at
The soil body is applied with an opposition, it is made to generate a reversed displacement S2；
The two superposition, final result is to lead to tunnel horizontal displacement coverage and tunnel maximum horizontal displacement value, respectively less than shield
Soil body S1 at structure tunnel surface；
(3) this method is while calculating the residual stress of the soil body at foundation pit enclosure structure bottom plane, it is also contemplated that power is downward
The frictional resistance of building enclosure side wall influences when transmitting；
(4) this method will calculate the shift value of half of tunnel surface of neighbouring foundation pit side, makes a concrete analysis of the change in displacement in tunnel, obtains
To the horizontal direction convergency value in tunnel；
Specifically comprise the following steps:
Step 1) establishes computation model:
1., 2., 3. and 4. the number of four side walls of foundation pit is respectively；
Foundation pit length L, unit symbol mm；
Foundation pit width B, unit symbol mm；
From foundation pit central point o transversely and horizontally with a distance from be x, be 1. positive with o point to side wall, unit symbol mm；
It is y with a distance from vertical equity from o point, is 3. positive with o point to side wall, unit symbol mm；
Distance d of the excavation of foundation pit face bottom to foundation pit enclosure structure bottom surface0, unit symbol mm；
The minimum clear distance s, unit symbol mm of excavation face and tunnel；
Foundation pit enclosure structure depth H, H=d+d0, unit symbol mm；
Vertical distance h, unit symbol mm of the ground to tunnel bottom；
Tunnel outer diameter D, unit symbol mm；
Calculation assumption:
(1) soil body is homogeneous, elastic half-space, and tunnel axis is oriented parallel to the long side of rectangle foundation pit；
(2) time and the space factor for not considering excavation of foundation pit, do not consider precipitation；
(3) it being discharged when excavation of foundation pit to will lead to resistance to shear of soil when cheating bottom, being converted into and applying straight up at the baseplane of hole
Evenly load γ d；
(4) foundation pit surrounding side wall can generate stress release after excavation, be equivalent to apply the triangle level into hole in side wall
To distributed load β K0γz；
(5) do not consider that tunnel has the influence calculated additional stress of soil；
(6) by considering that the foundation pit side-wall far from tunnel side discharges stress, to replace tunnel stiffness；
Step 2), hole bottom unloading analysis:
Due to the protective effect of bottom of foundation ditch building enclosure, the stress for forming shielding effect, therefore cheating bottom release, which will receive, goes along with sb. to guard him knot
The side friction that structure generates influences, the side friction calculation formula are as follows:
qs=c+K0σztanφ；
In formula:
qsFor unit equivalent entity side friction, unit symbol Pa；
C is the cohesive strength of soil, unit symbol Pa；
σzFor the soil stress at the arbitrary face at Foundation Pit bottom to building enclosure bottom, unit symbol Pa；
φ is the internal friction angle of soil, and unit symbol is °；
According to actual condition, it is changed to average side friction calculation formula are as follows:
qs1=c+1/2 (γ d+ γ H) K0tanφ；
In formula:
qs1Mean unit side friction, unit symbol Pa；
The then equivalent load that the soil body is subject at the horizontal plane of foundation pit enclosure structure bottom surface are as follows:
In formula:
σ is the equivalent load that the soil body is subject at the horizontal plane of foundation pit enclosure structure bottom surface, unit symbol Pa；
α is residual stress coefficient；
By the basic displacement solution of Mindlin vertical load, by integral, certain point (ξ, η) on horizontal plane at the building enclosure bottom surface
Unit force σ d ξ d η effect under, certain point (x on the outside of caused tunnel1,y1,z1) horizontal displacementWith vertical displacementRespectively
Are as follows:
In formula:
ξ is that certain puts abscissa, unit symbol mm on horizontal plane at building enclosure bottom surface；
η is that certain puts ordinate, unit symbol mm on horizontal plane at building enclosure bottom surface；
μ is the Poisson's ratio of soil；
G is the coefficient of rigidity of soil,Unit symbol is Pa；
EsFor the compression modulus of soil, unit symbol Pa；
Step 3), foundation pit side-wall unloading analysis:
It is foundation pit side-wall Triangle Load Distribution 1. in number by integrating by the basic displacement solution of Mindlin horizontal loading
In certain point (η, τ) unit force β K0Under γ d η d τ effect, cause certain point (x on the outside of tunnel1,y1,z1) horizontal displacementWith
Vertical displacementIt is respectively as follows:
In formula:
τ is the ordinate of certain point in the foundation pit side-wall Triangle Load Distribution of number 1., unit symbol mm；
In the case where number is foundation pit side-wall Triangle Load Distribution effect 2., cause certain point (x on the outside of tunnel1,y1,z1) water
Prosposition movesWith vertical displacementIt is respectively as follows:
In formula:
In the case where number is foundation pit side-wall Triangle Load Distribution τ effect 3., cause certain point (x on the outside of tunnel1,y1,z1) water
Prosposition movesWith vertical displacementIt is respectively as follows:
In formula:
In the case where number is foundation pit side-wall Triangle Load Distribution effect 4., cause certain point (x on the outside of tunnel1,y1,z1) water
Prosposition movesWith vertical displacementIt is respectively as follows:
In formula:
Step 4), total calculation formula:
Using principle of stacking, the unloading stress generated by Foundation Pit bottom and surrounding side wall is obtained, it is a certain on the outside of caused tunnel
Point (x1,y1,z1) horizontal total displacement SxWith vertical total displacement SzIt is respectively as follows:
To accurately calculate caused tunnel lateral displacement under Foundation Pit bottom load and surrounding side wall load action, take towards base
The half side tunnel of side is cheated, respectively several points, calculate separately the shift value of this several points, finally take average shift value as tunnel
Road shift value.
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